Prototype with single host server and no admin panel (#2)

Reviewed-on: wrenn/sandbox#2
Co-authored-by: pptx704 <rafeed@omukk.dev>
Co-committed-by: pptx704 <rafeed@omukk.dev>

envd/internal/shared/keys/hmac_sha256.go

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package keys
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+)
+
+type HMACSha256Hashing struct {
+	key []byte
+}
+
+func NewHMACSHA256Hashing(key []byte) *HMACSha256Hashing {
+	return &HMACSha256Hashing{key: key}
+}
+
+func (h *HMACSha256Hashing) Hash(content []byte) (string, error) {
+	mac := hmac.New(sha256.New, h.key)
+	_, err := mac.Write(content)
+	if err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(mac.Sum(nil)), nil
+}